Objectives—To determine the sensitivity of bacteriologic
culture of pooled fecal samples in detecting
Mycobacterium paratuberculosis, compared with bacteriologic
culture of individual fecal samples in dairy
Study Design—Cross-sectional study.
Animals—24 dairy cattle herds.
Procedure—Individual and pooled fecal samples
were submitted for bacteriologic culture, and results
were compared between these groups.
Results—Ninety-four and 88% of pooled fecal samples
that contained feces from at least 1 animal with
high (mean, ≥ 50 colonies/tube) and moderate (mean,
10 to 49 colonies/tube) concentrations of M paratuberculosis,
respectively, were identified by use of
bacteriologic culture of pooled fecal samples.
Prevalences of paratuberculosis determined by bacteriologic
culture of pooled and individual fecal samples
were highly correlated.
Conclusions and Clinical Relevance—Bacteriologic
culture of pooled fecal samples provided a valid and
cost-effective method for the detection of M paratuberculosis
infection in dairy cattle herds and can be
used to estimate prevalence of infection within a
herd. (J Am Vet Med Assoc 2003;223:1022–1025)
Objective—To determine efficacy and safety of a
commercial modified-live canine distemper virus
(CDV) vaccine used for prophylaxis in domestic ferrets.
Animals—Sixteen 16-week-old neutered male ferrets.
Procedures— Equal groups of ferrets were inoculated
subcutaneously at 16 and 20 weeks of age with
saline (0.9% NaCl) solution or a vaccine derived from
the Onderstepoort CDV strain and attenuated in a primate
cell line. Live virulent CDV was administered to
all ferrets intranasally and orally 3 weeks after the second
inoculation. Clinical signs and body weights were
monitored regularly during the study. Blood samples
for serologic examination were drawn prior to each
inoculation, before challenge exposure, and 10, 15,
and 21 days after exposure. Blood samples for
reverse transcriptase polymerase chain reaction (RT-PCR)
were obtained 5 days after the first vaccination,
and 5, 10, 15, and 21 days after challenge exposure.
Results—After challenge exposure, control ferrets
had significantly more clinical signs and weight loss,
compared with vaccinates. All vaccinated ferrets survived,
whereas all control ferrets died. The RT-PCR
assay was successful in detecting CDV in blood and
fresh or formalin-fixed tissues from infected ferrets.
Conclusions and Clinical Relevance—Findings suggest
that the vaccine when given SC to domestic ferrets
as directed is safe and protective against challenge
exposure with virulent CDV. The RT-PCR assay
may simplify detection of CDV in fresh and fixed tissues.
(Am J Vet Res 2001;62:736–740)
Objective—To determine whether flies can acquire
porcine reproductive and respiratory syndrome virus
(PRRSV) and disperse the virus throughout a designated
Animals—60 four-month-old pigs.
Procedure—On day 0, 28 of 60 pigs were inoculated
with PRRSV MN 30-100 (index variant). On the same
day, 100,000 pupae of ochre-eyed houseflies and
100,000 pupae of red-eyed (wild-type) houseflies
were placed in the swine facility for a release-recapture
study. Flies were recaptured at 2 locations within
the swine facility, 6 locations immediately outside
the facility, and 30 locations 0.4, 0.8, 1.3, 1.7, 1.9, and
2.3 km from the facility. Traps were emptied on days
2, 7, 8, 10, and 14. Samples derived from flies were
tested by use of a polymerase chain reaction assay,
virus DNA was sequenced, and viruses were tested
for infectivity by means of a swine bioassay.
Results—PRRSV RNA homologous to the index
PRRSV was detected in trapped flies collected inside
and immediately outside the facility and from 9 of 48
samples collected at 0.4 km, 8 of 24 samples collected
at 0.8 km, 5 of 24 samples collected at 1.3 km, and
3 of 84 samples collected at > 1.7 km from the facility.
Two samples collected at 0.8 km contained genetically
diverse variants of PRRSV. Swine bioassays
revealed the virus in flies was infectious.
Conclusions and Clinical Relevance—Flies
appeared to become contaminated with PRRSV from
infected pigs and transported the virus ≥ 1.7 km. Flyborn
transmission may explain how PRRSV is seasonally
transported between farms. (Am J Vet Res 2004;65:1284–1292)
Objective—To evaluate the influences of animal age, bacterial coinfection, and porcine reproductive and respiratory syndrome virus (PRRSV) isolate pathogenicity on virus concentration in pigs.
Animals—Twenty-one 2-month-old pigs and eighteen 6-month-old pigs.
Procedure—Pigs were grouped according to age and infected with mildly virulent or virulent isolates of PRRSV. The role of concurrent bacterial infection was assessed by infecting selected pigs with Mycoplasma hyopneumoniae 21 days prior to inoculation with PRRSV. On alternating days, blood and swab specimens of nasal secretions and oropharyngeal secretions were collected. On day 21 after inoculation with PRRSV, selected tissues were harvested. Concentrations of PRRSV were determined by use of quantitative real-time PCR and expressed in units of TCID50 per milliliter (sera and swab specimens) or TCID50 per gram (tissue specimens).
Results—Concentrations of virus were higher in blood and tonsils of pigs infected with virulent PRRSV. Pigs infected with virulent PRRSV and M hyopneumoniae had significantly higher concentrations of viral RNA in lymphoid and tonsillar tissue. Coinfection with M hyopneumoniae resulted in a higher viral load in oropharyngeal swab specimens and blood samples, independent of virulence of the PRRSV isolate. Two-month-old pigs had significantly higher viral loads in lymph nodes, lungs, and tracheal swab specimens than did 6-month-old pigs, independent of virulence of the PRRSV isolate.
Conclusions and Clinical Relevance—Multiple factors affect PRRSV concentration in pigs, including pathogenicity of the PRRSV isolate, age, and concurrent infection with M hyopneumoniae.